ULTRASTRUCTURAL INVESTIGATION OF THE SECONDARY EXCRETORY SYSTEM IN DIFFERENT STAGES OF THE PROCERCOID OF TRIAENOPHORUS-NODULOSUS (CESTODA, PSEUDOPHYLLIDEA, TRIAENOPHORIDAE)

The formation of the definitive procercoid excretory system of the pse udophyllidean cestode Triaenophorus nodulosus has been investigated. T his process can be divided into 3 main stages. In the first stage, act ive autophagic processes lead to the formation of intracellular excret ory canals. In the second stage, the process of the autolysis is enhan ced and the system of intercellular lacunae functioning as an excretor y system is formed. A definitive excretory system of the procercoid fo rms at the next stage, by means of the migration and proliferation of undifferentiated cells replacing the lacunar system.